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Danny Duffy Tests Out a Slider

It’s February 27. The Royals had their first spring training game of 2014, and this early into the season, there aren’t many conclusions to be drawn.

Nonetheless, each game brings more information than we’d had before, and in Thursday’s game, we learned that Danny Duffy is at least attempting a significant adjustment.

As reported by Andy McCullough of the Kansas City Star, Duffy was approached about using a slider – a pitch that he could have better command of – as his primary breaking ball rather than the curveball he’s primarily used since breaking into the big leagues. For reference, since Duffy’s MLB debut in 2011 through the end of 2013, he was primarily a three pitch pitcher, using a fastball (60.59% of the time), curveball (18,16%) and changeup (13.9%). In that same time span, he threw a slider 2.23% of the time and a cutter 0.65% of the time.

Of his three primary pitches, Duffy’s curveball was the one most likely to be called a ball. In some ways, that’s inevitable since pitchers will try to bury a curveball in the dirt when ahead, but even in other situations, it would be apparent that Duffy would struggle with his curveball’s command.

His new approach (at least at this stage in spring training) is to turn a cutter into more of a slider:

Duffy’s primary breaking pitch today was a slider. He’s trying to reduce speed from his cutter, and increase the break.

Today’s pitch f/x data matches up. In those rare cases when Duffy would throw a cutter, it would clock in at an average velocity of 86.11 mph with some break, but not much:

From BrooksBaseball.net

Granted, the cutter’s data is about as small of a sample as you can get, but for illustration of the adjustment, I think it’s fine.

On Thursday, he threw six sliders for an average of 80.6 mph, but with more break than in the past (again, the sample size caveat applies). Of his 37 pitches, he threw more sliders than curves or changeups.

Duffy’s one of the harder throwers on the team, with a fastball that averages around 94 mph, but can peak around 97. The slider, as noted by Clint Scoles, could be a better pitch for him because it’s closer to his fastball, and the difference in how the batter might see the pitch versus how they may see a curveball could make a big difference:

More velocity, less time for hitters to react with the appearance closer to the fastball. His curve should be nothing more than show me IMO

So there could be something to this adjustment. Duffy’s primary issue has been controlling his pitch count and finishing at bats. But if he has an easier time controlling a pitch, he should be able to throw it for strikes more often and hit his spots easier. Ideally, he can become more efficient that way and get deeper into games. He’s still going to be a strikeout pitcher, and he’s not likely to start throwing shutouts every night, but it could allow him to get his average innings per start up. Even going from five innings per start to six would help – that’s 30 innings or so the bullpen doesn’t have to worry about.

Of course, things can and do change at a moment’s notice, and one poor outing with the new slider could cause Duffy to scrap the project altogether. He’s far enough removed from Tommy John surgery that there shouldn’t be heightened concern about throwing a slider (and that the Royals asked him to try it suggests they’re not concerned that it’s a risk), but any complication could halt the experiement as well. But over the course of March, this will be something to keep an eye on.

Update (3/6): Brooks has Duffy throwing nine sliders out of 40 pitches in his second appearance of spring, a 3/4 game against the Reds in spring training.